1. Field of the Invention
The present invention relates to a wiring substrate and a semiconductor package.
2. Description of the Related Art
Recently, a wiring substrate has been provided for mounting a semiconductor device such as a light emitting device or the like. For example, a wiring substrate is known in which a wiring is formed on a heat spreader via an adhesion layer. In such a wiring substrate, when heat is generated by a semiconductor device that is mounted on the wiring, it is necessary to transfer the heat to the heat spreader. At this time, as the adhesion layer functions as a part of a radiation path, a material with a high coefficient of thermal conductivity such as insulating resin including alumina filler or the like is used as the adhesion layer.
However, as the wiring and the heat spreader are electrically-conductive materials, if the adhesion layer is made thin (about 50 μm, for example), there is a possibility that the wiring and the heat spreader are not sufficiently insulated. Thus, it is necessary to form the adhesion layer to have a thickness of about 100 to 200 μm. On the other hand, although the wiring and the heat spreader are sufficiently insulated by forming the adhesion layer to have the thickness of about 100 to 200 μm, in such a case, there is another problem that a thermal radiation property becomes lower due to the increase of heat resistance of the adhesion layer.
As described above, it is difficult for a conventional wiring substrate for mounting a heat generation semiconductor device such as a light emitting device or the like to ensure an insulation property and to improve a thermal radiation property at the same time.